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  • demography  (2)
  • Brachionus patulus  (1)
  • 1
    ISSN: 1573-5117
    Keywords: Rotifera ; Brachionus patulus ; DDT ; sublethal effects ; life history parameters ; demography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The combined effects of sublethal levels of DDT (0, 15, 30, 45, and 60 µg·l−1) and food (Chlorella at 1 and 3 × 106 cells ml−1) on the demography of the rotifer Brachionus patulus were studied. The average lifespan, life expectancy, net reproductive rate (Ro) and intrinsic rate of increase (r) were significantly greater at the higher food level, but declined with increasing DDT concentration. A significant DDT food interaction was manifested in the toxicity-mitigating action of the higher food density at higher DDT levels. The r values were negative at DDT levels 30 µg · l−1 and above, only when food density was low. The effective DDT concentration at which a given parameter value was reduced to 50% of that in the controls (EC50) was lower at lower food levels for both survivorship and reproduction, and lower for reproduction than for survivorship at either food level.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 435 (2000), S. 117-126 
    ISSN: 1573-5117
    Keywords: demography ; Chlorella density ; Ceriodaphnia cornuta ; Moina macrocopa ; Pleuroxus aduncus ; Simocephalus vetulus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Algal food density is known to influence life history variables of cladoceran species. It is not, however, well established whether both littoral and planktonic cladocerans show similar trends when exposed to increasing food concentrations. In the present work, we studied the life table demography of four cladoceran species (Ceriodaphnia cornuta, Moina macrocopa, Pleuroxus aduncus and Simocephalus vetulus) in relation to three algal food concentrations (low: 0.5 × 106, medium: 1.5 × 106 and high: 4.5 × 106 cells ml−1 of Chlorella vulgaris) (in terms of carbon content, these were equivalent to 0.15, 0.45 and 1.35 μg ml−1, respectively) at 25 °C. In general, for all the tested cladoceran species, values of average lifespan, gross reproductive rate, net reproductive rate, generation time and the rate of population growth were higher at lower food concentrations. Furthermore, high food concentration resulted in a negative population growth rate (mean ± standard error: −0.091 ± 0.026) for P. aduncus. The highest population growth rate (0.602 ± 0.014) was recorded for M. macrocopa at low food density. S. vetulus had the longest average lifespan (40 ± 1 d) while M. macrocopa had the lowest (5 ± 1 d). C. cornuta showed better performance at medium food concentration. We conclude that among the algal concentrations used here, 0.5 × 106 – 1.5 × 106 was beneficial not only to the planktonic species but also to the littoral P. aduncus and S. vetulus while 4.5 × 106 cells ml−1 was unsuitable for all the cladocerans tested.
    Type of Medium: Electronic Resource
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